This invention relates to a device which filters, isolates, and contains for sampling or storage, the supernatant fluid from a mixture of immiscible liquids or a slurry which has been stratified by centrifuging or standing. More specifically, it relates to a new and improved means for processing blood serum specimens which are to be used in automatic clinical chemistry analyzers.
In order to understand the conditions and problems inherent in clinical laboratory practice, the following discussions are pertinent.
1. Clinical laboratories employing automatic analyzers frequently process hundreds of blood specimens per day. Each individual specimen can require a wide variety of determinations. Often, more than one type of analyzer is needed to achieve the desired analyses. Obviously, maintaining the identity of large numbers of specimens and correlating multiple test results with the proper parent specimen is a problem of great complexity and importance. Errors in sample identification may conceivably contribute to the death of a patient.
2. The automatic sampling modules of existing clinical analyzers are limited in several ways by mechanical considerations. For instance, the vessels containing serum to be aspirated by the sampler must be of uniform dimensions, particularly height, so that the sample probe can enter them and function properly. This situation is normally met by transferring serum specimens for sampling to a series of uniform sample cups contained in a suitable rack. A problem arises, however, from such a transfer of serum to a sample cup in that the new cup requires labeling in some form, and this creates a potential source of identification errors.
3. Any volume of each serum specimen remaining after analysis is routinely stored in the clinical laboratory for several days so that check analyses can be made if necessary. Under most circumstances, such remaining serum volumes are decanted into special individual containers for refrigerated storage. The problem again arises that this additional transfer can require a further labeling operation and create another source of potential identification errors.
4. Still another problem arises in that each transfer of serum from one vessel to another creates a potential for chemical contamination of the specimen. Moreover, each transfer by decanting or pipetting creates a potential for contaminating the technical personnel with diseased serum.
5. Automated clinical chemistry analyzers themselves are often a problem because they are especially susceptible to clogging by small particles. Even serum which has been centrifuged still requires filtering.
6. It is well known that blood serum should be completely isolated from blood cells as soon as possible because ionic and osmotic exchanges take place, across cell walls, between serum and cells. Incomplete or delayed isolation of these blood components raise a potential problem of inaccurate analytical results.